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991.
José Edson da Silva Valdinete Lins da Silva Maria da Conceição B.S.M Montenegro 《Analytica chimica acta》2004,506(2):197-202
A sequential injection analysis system was developed to quantify pH, chloride and nickel in electrolytic baths, in the ranges 1-5 pH units, and 0.1-1.0 and 0.1-1.6 mol l−1, respectively. To enable pH and chloride determination, potentiometric detection with two ion-selective electrodes in a tubular configuration was used. Nickel concentrations were assessed using colorimetric detection at 660 nm. pH was determined prior to nickel determination and just after sample injection (500 μl) into a 0.025 mol l−1 phosphate buffer carrier stream at pH 6.3 and a 9.10 ml min−1 flow rate. For chloride determination, on-line dialysis through a cellulose membrane was used to enable sample dilution and matrix separation. A 25−1 fractional factorial design based on the carrier solution composition and the levels of the hydrodynamic parameters was used for system optimization. At the optimized settings a sampling rate of 40 samples h−1 was attained, with precision and accuracy statistically indistinguishable from those achieved with conventional procedures. 相似文献
992.
This paper belongs to the class of works about perturbations of linear-quadratic control problems. Given a linear, bounded, surjective operatorL
o:BV, between Banach spaces, the problem of minimizing |u–|, B, among all the elementsu satisfying the constraintsL
o
u=y, has unique solutions under suitable hypotheses onB.The same occurs if we consider a sequence of operatorsL
n
:BV, which represent perturbations of theL
o-operator. Ifu
n
(, y) andu
o(, y) are the minima of the perturbed problem and the original problems, respectively, convergence ofu
n
tou
o is characterized by means of convergences ofL
n
and their adjoint operators, in the case whenV
l
.A sufficiency criterion is given whenB andV are Hilbert spaces. Finally, we study an example problem governed by an ordinary differential equation, in which convergence of the minima is characterized in terms of control coefficients.This work was supported by CNR-GNAFA, Rome, Italy. 相似文献
993.
Marie P. Cifuentes 《Journal of organometallic chemistry》2004,689(24):3968-3981
The authors’ studies of the nonlinear optical (NLO) properties of metal alkynyl complexes are summarized; structure-NLO property relationships are developed and attempts to “switch” optical nonlinearities of alkynyl complexes are described. 相似文献
994.
The relative error between best and worst solution of quadratic bottleneck assignment problems with cost coefficientsd
ijpq
=a
ip
b
jq
is considered, wherea
ip
is either arbitrarily given or corresponds to a distance in the plane. It is shown that the relative error is bounded by a function(m), tending to zero, with probability tending to one asm , provided the data are uniformly distributed. This implies that any algorithm for the above mentioned problems yields asymptotically an arbitrarily small relative error with probability tending to one. 相似文献
995.
Lingcui Zhang Yongfeng Ruan Yali Liu Ying Zhai 《Crystal Research and Technology》2013,48(11):996-1002
ZnO nanorod arrays have been successfully prepared on ITO substrate by a chemical‐bath deposition method at different growth temperatures. The influence of the growth temperature on the morphology and microstructure of the ZnO nanorods was investigated by scanning electron microscopy (SEM) and X‐ray diffraction (XRD). The results showed that the diameter of the ZnO nanorods decreased and the size of the nanocrystals increased with increasing growth temperature. Optical absorption measurements showed the absorption band edge has shifted to a lower‐energy region due to the quantum size effect. Green emission and UV emission bands were observed and they are found to be temperature dependent, which indicates that the deep‐level emission and band‐edge emission of ZnO nanorods is closely related to the rod diameter, and the related mechanism is discussed. 相似文献
996.
997.
When a consumed carbon anode in an aluminium electrolysis cell is replaced, the solid crust covering the anode and the bath is removed and transported in hopper cars to a cooling area where it remains for a period of one to four days, or more, to cool from a temperature of approximately 900°C to an acceptable temperature for autogenous milling, gas cleaning, product classification, and recycle to the process. This article addresses the possibility of processing the hot crust material more rapidly by using a separate or combined crushing/heat exchange system. Results of mechanical and thermal tests are presented and discussed. Mechanical tests demonstrated that it requires much less force to crush hot crust than cold crust samples. The thermal tests consisted of submitting both a single block and a bed of particles of the crust material to heating and cooling cycles to determine the convective heat transfer coefficient and the thermal diffusivity. The values obtained for the heat transfer coefficients were similar to those predicted by correlations, while the thermal diffusivity was larger than expected. Based on the results, a number of strategies to manage the crust material were proposed and analyzed from the perspectives of the plant conditions. Some of these options are briefly discussed and simulated. The results of the simulations indicate that in order to significantly reduce the cooling time, the size of the crust pieces should be reduced prior to cooling. 相似文献
998.
We derive rigorously the short-time escape probability of a quantum particle from its compactly supported initial state, which has a discontinuous derivative at the boundary of the support. We show that this probability is linear in time, which seems to be a new result. The novelty of our calculation is the inclusion of the boundary layer of the propagated wave function formed outside the initial support. This result has applications to the decay law of the particle, to the Zeno behaviour, quantum absorption, time of arrival, quantum measurements, and more. 相似文献
999.
1000.